Apple's stock instant-message program in Mac OS X is currently in its fourth release and has made steady improvements in competing with third-party chat programs to provide advanced functionality such as tabs, animated buddy icons, and utilities to assist the transfer of multiple files. At its heart, iChat is a dead simple way to connect with IM buddies on multiple networks including AIM, Google Talk, Jabber, and Bonjour. Missing, however, is support for other popular protocols such as Windows Live Messenger, IRC, and Yahoo Messenger.
Some of the standout features in the latest iteration of iChat include advanced video chat with animated backgrounds that let users step out of the frame and then be visually transposed as if they were actually in that location. There's also built-in support for screen sharing with other iChat users, as well as a conversation recording.
Winner: iChat (Apple.com/MacOSX/features/iChat)